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Converted Mode Seismic Survey Design

a seismic survey and conversion mode technology, applied in the field of geophysical prospecting, can solve the problems of sp survey being problematic to implement in the marine environment, the method and procedure used in designing common mode reflection seismology surveys are not directly applicable to designing converted mode reflection seismology surveys,

Active Publication Date: 2009-12-03
EXXONMOBIL UPSTREAM RES CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0024]Data from such a survey, after processing and interpretation, may indicate formations likely to contain hydrocarb...

Problems solved by technology

Methods and procedures used in designing common mode reflection seismology surveys are not directly applicable to designing converted mode reflection seismology surveys.
Consequently, though the practice of design of common mode seismic surveys to achieve specified seismic image resolution is well established, the same is not true for converted mode seismic surveys.
The SP survey has been problematic to implement in the marine case.

Method used

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  • Converted Mode Seismic Survey Design
  • Converted Mode Seismic Survey Design
  • Converted Mode Seismic Survey Design

Examples

Experimental program
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Effect test

example 1

[0079]A PS converted wave seismic survey is desired to image a depth of 3000 meters over a square area that is 4000 meters on each side, the sides of the square aligned along east-west and north-south directions. The survey orientation is such that source and receiver offsets have predominantly east-west and west-east azimuths. The earth is well approximated by a layered compressional velocity model given by a propagation velocity of 1500 meters per second from the surface to a depth of 1000 meters, 2000 meters per second from 1000 to 2000 meters depth, and 2500 meters per second below 2000 meters depth; and a layered shear velocity model given by a propagation velocity of 500 meters per second from the surface to a depth of 1000 meters, 1000 meters per second from 1000 to 2000 meters depth, and 1500 meters per second below 2000 meters depth. No independent information on the energy distribution with scattering angle is available, nor has any range of incident angles been specified ...

example 2

[0102]This example is the same as Example 1, except it has been specified that the maximum offset to be acquired for the survey is 3000 meters, and that this offset contains more converted mode seismic energy than smaller offsets. Since scattering angle is related to offset, the maximum offset sets the maximum scattering angle that will be acquired.

[0103]i) Determine the Bandwidth Required to Achieve the Specified Vertical to Seismic Resolution at the Target Depth.

[0104]In this case, the offset of 3000 meters has been identified as the maximum offset to be acquired by the survey and that this offset contains the most converted mode energy. Therefore, the survey designer has chosen to base the bandwidth requirement on the 3000 meter offset.

[0105]First, the scattering angle that corresponds to an offset of 3000 meters is determined by ray tracing. A 3000 meter offset from specular reflection off a horizontal reflector at the target depth corresponds with a scattering angle of 69.0°. T...

example 3

[0115]This example is the same as Example 2, except it has been specified that only east-west orientations of source—receiver pairs will be acquired for imaging. The solutions to steps i) and iii) are the same as in Example 2 and are not repeated for Example 3. But the aperture solution in step ii) is different than Example 2 because both east-west and west-east orientations of source—receiver pairs were required for imaging in Example 2, but only east-west orientations of source—receiver pairs will be acquired for imaging in Example 3.

[0116]i) Determine the Bandwidth Required to Achieve the Specified Vertical Seismic Resolution at the Target Depth.

[0117](Solution is given in step i) of Example 2)

[0118]ii) Determine the Migration Acceptance Angle and Corresponding Source and Receiver Apertures Required to Achieve the Specified Lateral Seismic Resolution at the Target Depth.

[0119]The minimum required migration acceptance angle is determined by

θa≈arcsinRvRlm.

[0120]Evaluating, the requ...

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Abstract

Method for designing a converted mode (PS or SP) seismic survey to accomplish specified vertical and lateral resolution objectives at target depth. An equation (181) is provided for determining the minimum bandwidth required for a desired vertical resolution at a selected scattering angle, as a function of incident and reflected wave velocities, one of which is the P-wave velocity and the other is the S-wave velocity. A second equation (182) is provided for determining migration acceptance angle from the desired vertical and lateral resolutions. Source and receiver apertures may then be determined by ray tracing. Finally, a third equation (183) is provided for the maximum bin size to avoid aliasing, given the migration acceptance angle and a maximum frequency needed to achieve the bandwidth requirement. Source and receiver spacing may then be based on the maximum bin size.

Description

[0001]This application claims the benefit of U.S. Provisional application 60 / 839,209 which was filed on Aug. 22, 2006.FIELD OF THE INVENTION[0002]The invention relates generally to the field of geophysical prospecting and, more particularly, to designing seismic reflection surveys of subterranean regions. Specifically, the invention is a method for designing a converted mode seismic survey to accomplish specified resolution objectives with efficient utilization of survey source and receiver equipment.BACKGROUND OF THE INVENTION[0003]The method of reflection seismology is an important tool used to image or determine properties of the earth. The method generally includes a source, or distribution of sources, usually on or near the earth's surface that excites a seismic wave into the earth; and a receiver, or distribution of receivers, that records the wave that is reflected (or scattered) back from the earth. Many different types, or modes, of seismic waves are known. The compressiona...

Claims

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Application Information

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IPC IPC(8): G01V1/28G01V1/36
CPCG01V1/284
Inventor MEIER, MARK A.
Owner EXXONMOBIL UPSTREAM RES CO
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